H2N2 as a Potential Pandemic Threat

According to a new study published in the Journal of Virology, descendants of the H2N2 strain of avian influenza, last seen in humans in the 1950s, may still pose a significant threat to humans, particularly those under 50 years of age. According to the study, conducted by St. Jude’s Children’s Research Hospital, the virus is still highly adapted to human respiratory cells. The last major outbreak occurred in 1957-58, and killed up to two million people globally. However, effective antivirals were absent at the time – should the virus, which has subsequently circulated in birds, re-emerge, it should be susceptible to modern antivirals. However, as the virus has not been seen in humans in over 50 years, anyone under the age of approximately 55 years would constitute a naive host, and as there are 230 million people in the US alone currently under the ages of 55, the size of this naive population is not insignificant.

From Science Daily – “‘While these viruses genetically look very avian, this study shows they can behave like mammalian viruses and replicate in multiple mammalian models of flu,’ said the study’s first author, Jeremy Jones, Ph.D., a postdoctoral fellow in Webster’s laboratory. ‘That is troubling because some of the original H2N2 pandemic viruses looked avian when the pandemic began in 1957, but in a few short months, all of the isolated viruses had picked up the genetic signatures of adaptation to humans. Our results suggest the same could happen if the H2N2 viruses again crossed from birds into humans.’ Work is underway at St. Jude to identify other changes that are critical to the ability of avian flu viruses to infect and replicate in mammalian cells, Jones said.”